The present invention relates to a method of forming complex features and fine details in work pieces made of Carbon-Carbon (Cxe2x80x94C) composite material and other carbon-containing materials. The present invention also relates to heat exchangers and fuel cells formed of carbon-containing materials.
Carbon-Carbon composite materials are used in certain heat exchangers and fuel cells. Consider a Carbon-Carbon plate-fin heat exchanger core including a stack of plates and fins. The plates may be made from flat thin-gauge two-dimensional Carbon-Carbon woven fabrics, and the fins may be made from thin-gauge two-dimensional Carbon-Carbon woven fabrics that are corrugated. Thickness of the plates and fins may range between about 0.1 millimeters and 1 millimeter.
Fabricating the Carbon-Carbon fins can be both difficult and time consuming. The fins define long, narrow channels that function as fluid passageways. Because many fins have complex shapes, creating a high density of fins (i.e., x number of fins per linear inch) is even more difficult. Yet it is extremely desirable to increase the fin density in order to increase the heat transfer capability of the heat exchanger.
Carbon-Carbon bipolar plates of proton exchange membrane fuel cells are typically flat, having a thickness of about 0.2-1 millimeters and, in addition, having intricately shaped, fine-featured flow fields for channeling the flow of the hydrogen and oxygen gases used in the operation of the fuel cells. These flow fields typically have defined features of submillimeter dimensions. Forming such fine detailed features is extremely difficult.
Complex shapes and fine details in a carbon-containing work piece are formed using photolithographic etching methodology. A layer may be formed in a specific pattern on one or both sides of the work piece. Selective etching of the exposed portions of the work piece creates the desired features in the work piece.